Punch for manufacturing flexible conical tubes

ABSTRACT

The invention relates to a method of manufacturing flexible metal tubes of frustoconical shape. A semi-finished tube is initially produced by inverse-impact extrusion with a conical punch whose outer surface is provided with one or more helical projecting ridges; the semi-finished tube is then finished on a smooth-walled conical mandrel.

' United States Patent [191 Michel June 24, 1975 PUNCH FOR MANUFACTURING FLEXIBLE CONICAL TUBES [75] Inventor: Phlippoteau Michel, SMaur, France [73] Assignee: Scal (Societe de Conditionnement en Aluminum), Paris, France [22] Filed: June 6, 1974 [21] Appl. No.: 476,868

Related US. Application Data [62] Division of Ser. No. 309,773, Nov. 27, 1972, Pat. No.

[30] Foreign Application Priority Data Nov. 25, 1971 France 71.42251 52 us. Cl 72/273; 72/469 51 1m. (:1. B21C 25/00 58 Field of Search 72/256, 267, 262, 370,

[5 6] References Cited UNITED STATES PATENTS 2,096,018 10/1937 Wright 72/267 3,267,712 8/1966 Atkin 72/264 3,839,890 10/1974 Philippoteau 72/68 Primary Examiner-C. W. Lanham Assistant Examiner-Robert M. Rogers 57 ABSTRACT The invention relates to a method of manufacturing flexible metal tubes of frustoconical shape. A semifinished tube is initially produced by inverse-impact extrusion with a conical punch whose outer surface is provided with one or more helical projecting ridges; the semi-finished tube is then finished on a smoothwalled conical mandrel.

6 Claims, 4 Drawing Figures Fig. I

PATENTEDJUN24 I975 99 22 SHEET 3 Fig. 4

l I I I I I I l I I l I I I l i PUNCH FOR MANUFACTURING FLEXIBLE CONICAL TUBES This is a division of application Ser. No. 309,773, filed Nov. 27, 1972, now US. Pat. No. 3,839,890.

This invention relates to a method of manufacturing flexible metal tubes of frustoconical shape.

Flexible metal tubes of the type described, used for packaging pasty materials, have been known for some time.

They are generally manufactured by cold extrusion (also known as inverse impact extrusion) of metal pellets, with an increasing preference for the use of aluminum and its alloys.

Unfortunately, such tubes, which are extremely con venient to use, are confronted by a number of major disadvantages before they are filled. Due to the fact that they are fabricated by cold extrusion, they are cy lindrical in shape and transportation from the facility where they are made to the facility where they are filled calls for bulky packages, generally made of cardboard, since each of the unfilled tubes, which are sensitive to even the most gentle impact, have to be placed in a sepv arate compartment. As a result, transportation and storage costs add considerably to the price of the tubes.

Accordingly, it was proposed to provide the flexible metal tubes with a slight frustoconical shape to enable them to be nested one within the other. The result expected was two-fold, namely, a reduction in the volume of the package and a reduction in the risk of damage to the tubes.

In one known process for obtaining conical shape, the tubes were placed in a conically shaped die and expanded by means of an inflatable membrane or even by the direct introduction of air, the orifice of the tube being plugged by means of a frustoconical member advancing at a rate commensurate with the expansion of the filling opening. However, the tapering of an annealed cylindrical tube involves some amount of cold working of the metal, which makes it all the more difficult to form the fold by which the tube is closed, because this operation is carried out in the most heavily cold-worked zone, i.e. in the zone surrounding the filling opening, and because the metal has to remain elastic in use.

In addition, to carry out this operation, an additional machine has to be introduced into the already long chain leading from the metal blank to the final tube ready for packaging. 7

Any thought towards tapering the tube directly during its formation is hampered by the fact that it is not possible to make use of a conical punch because, during impact extrusion, the metal flows through an annular orifice between the punch and the matrix, ascending parallel to the axis of the punch with a clearance of about one-tenth of a millimeter from its wall. This clearance is necessary in order to insure that, during cooling of the metal as it leaves the extrusion die, there will be no shrinkage onto the punch itself.

The resulting friction would stop free flow and extrusion would be uncontrollable. Accordingly, it is obvious that a conical punch would not permit such flow of the metal parallel to the wall of the punch.

Attempts have also been made to lubricate the extruded product on the punch during extrusion, as by means of a stream of compressed air introduced under high pressure from inside the punch through openings situated at the level of the extrusion edge. The number of malformations obtained by this method and the particularly large number of longitudinally split tubes prevents practical use of this process.

Attempts have been made to obtain a taper during extrusion. To this end, the punch is provided over part of its height with circular ridges having envelopes which widen from the head of the punch to form a frustum, the axis of which coincides with the axis of the punch.

Unfortunately, this process allows only a limited number of ridges to be used because each causes a sudden increase in diameter and, hence, a degree of resistance which increases with the increase in the projection of the ridge. Ultimately, the individual resistances combine to exceed the strength of collapse of the flexible tube during extrusion so that the tube concertinas.

It is thus practically impossible to provide the taper of the tubes with an angle sufficiently wide to enable them to be nested one in the other with a clearance (i.e. a gap between two successive edges) of about 20 mm, substantially corresponding to the height of the tip and of the plug.

It is an object of this invention to enable at least a semi-finished frustoconical metal blank to be produced by inverse-impact extrusion.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings in which FIG. 1 is a sectional elevational view which diagrammatically illustrates an arrangement for carrying out the method of this invention;

FIG. 2 is an enlarged sectional view taken through a ridge of the punch;

FIG. 3 is an elevational view of an apparatus for smoothing the blank to complete the operation; and

FIG. 4 is an elevational view, partially in section, which shows a modification of the punch enabling the tube to be smoothed during extrusion.

The invention relates to a method of manufacturing flexible, frustoconical tubes from a metal blank by inverse-impact extrusion, carried out with a punch provided over at least a part of its height, with at least one helical projecting ridge, the cross section of which widens from the head of the punch to form a frustum whose axis coincides with the axis of the punch.

The opening angle of this frustum is generally between l and 2 although, for tubes of very large diameter and considerable length, it can be greater than 2.

The gradient which the helical ridge forms with a plane perpendicular to the longitudinal axis of the punch is of the order of 20.

The distance between two successive passages on a generatrix of one or more parallel helical ridges is between 12 and 20 mm.

The blank obtained by extrusion with the punch described is smoothened on a smooth-walled frustoconical mandrel.

Smoothing can be carried out by means of a tool over which the blank has to pass to a subsequent operation normally intended for finishing purposes such as, for example, trimming, external lacquering, etc.

Smoothing can also be carried out during the extrusion operation itself. In this event, use is made of a punch at least the outer portion of which can be rotated.

The invention also relates to the tubes formed by the method described above.

The arrangement diagrammatically illustrated in FIG. 1 comprises a die 1 of the kind normally used for forming flexible metal tubes by inverse-impact extrusion. The punch 2 is slightly frustoconical in its general shape, corresponding to the taper with which it is required to provide the tube. The opening angle of these tubes is normally between 1 and 2, i.e. the angle formed by a generatrix with the longitudinal axis is between 30 and I". In the case of tubes of very large diameter and considerable length, this angle can be greater than 2.

At its base, the punch 2 comprises an annular extrusion ridge 3 whose function is well known. After extrusion, the metal cools and, as a result, shrinks. Accordingly, allowance has to be made for this shrinkage by increasing the diameter of the punch, depending upon the coefficient of expansion of the metal at the temperature in question. In the case of conventionally produced components, this increase varies between 0.05 and 0.1 mm.

This clearance between the extruded metal and the punch should be maintained over the entire length of the conical punch. According to this invention, this result is obtained by means of one or more helical ridges 4. The angle a, which this helix forms with a plane perpendicular to the longitudinal axis of the punch, is preferably of the order of about 20.

On the other hand, it is essential that the extruded metal should not at any time come into contact with the wall of the punch between two helical ridges. Thus, the vertical projection of the base of one ridge always comes within the ridge immediately beneath it along a given generatrix of the punch.

Accordingly, several helical ridges may optionally have to be distributed uniformly over the periphery of the punch in such a way that the distance between two helices is between 12 and 20 mm, as measured perpendicularly to the helices inclined at about 20 to the horizontal.

A second parameter for determining the number of parallel ridges is the height of these ridges which, incidentally, is constant over the entire length of the punch. FIG. 2 is a section through one ridge serving as an example. It is similar in shape to a trapezium, although it should be pointed out that the base of this trapezium forms a certain angle with the axis of the punch while the minor base is substantially parallel to the axis of the punch. The height x of this pseudo-trapezium, i.e. the height of the ridge, can vary within the range of 0.2 and 0.5 mm. In the example selected, it is 0.3 mm.

During extrusion, the metal advances in the direction of arrow 5 (from the bottom of FIG. 2) and encounters a ridge. The selection of the angle b, determining the gradient of the oblique side 6 which diverts the flow, is very important. The inclination of this side should be such that the metal can slide over it quickly, i.e. without prolonged contact. An angle of about 25 has given good results in practice. The width of the minor base should be as reduced as possible while the slope of the second oblique side has no real bearing upon the operation of the machine. These parameters are determined essentially by the type of material of which the punch is made and the methods by which it is machined.

It is now simple to understand the method of the invention.

A blank, placed in the die 1, is flattened by the punch 2 under a calculated impact. The metal (for example aluminum) flows along the punch 2 to form the tube 7. The tube issues through the gap left between the extrusion edge 3 and the die 1, and is directed parallel to the axis of the punch 2 until it comes into contact with a ridge 4 which it does gradually, generatrix by generatrix, by virtue of the helical shape of this ridge.

The included surface 6 of the ridge 4 diverts the flow of metal to the top of the ridge where it returns to its original direction parallel to the axis of the punch 2 until it comes into contact with the following ridge. These contacts and diversions take place step by step so that the metal is not subjected to any appreciable peripheral stressing and the diameter of the tube gradually increases.

Upon completion of the operation, the semi-finished tube 7 is removed from the punch 2, having one or more helical bands joined together by shoulders.

This appearance is not acceptable, either from the aesthetic point of view or from the technical point of view, because the shoulders would prevent the tubes from being stacked in telescoping relation.

Accordingly, the tube has to be subjected to a smoothing operation. There is no need to bring another machine into the production line to carry out this operation because this work can be carried out simultaneously with one of the finishing operations normally provided in existing production lines, for example during trimming of the skirt, deburring of the rod or screwthreading of the orifice.

To carry out this operation, the semi-finished tube 7 is placed on a mandrel 8 with the same conical form as the interior of the finished tube. This mandrel 8 is rotated by means of the pulley wheel 9. One or more rollers, mounted for free rotational movement on a spindle 11 parallel to the generatrix of the mandrel 8, are moved axially by any type of suitable mechanism (not shown in the drawing). Under the effect of the rollers 10, the shoulders between the helical bands are removed as by ironing out. Upon completion of the operation (see FIG. 3), the tube has the smooth frustoconical form required.

A modification of the embodiment described above enables smoothing to be carried out during the actual tapering operation (see FIG. 4). To this end, the punch 12 comprises a cylindrical core 13 which must be strong enough to be able to carry out impact extrusion. It is widened at its free end to form the complete impact surface 14, including the extrusion edge 3. This widening results in the formation of a ledge 15 which acts as a support for a sleeve 16.

The outside of this sleeve 16 is shaped in the same way as the punch 2; in other words, its outer surface is slightly frustoconical, and it comprises one or more helical ridges 4. The inner surface of this sleeve 16 is cylindrical. The sleeve as a whole is mounted for rotational movement about the core 13.

At its end opposite to the ledge 15, the sleeve 16 carries a pulley wheel which is driven, for example, by a motor 18 or by any other type of suitable drive means.

During extrusion, the sleeve is rotated at high speed and the helical irregularities are immediately removed so effectively that the tube does not have to be smoothed off.

This embodiment is only one example. Other methods utilizing the rotation of all or part of the punch.

could also be used.

It will be understood that changes may be made in the details of construction and operation without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. A punch for manufacturing flexible metal tubes of frustoconical shape from a metal blank by inverseimpact extrusion in which the punch has axially spaced helical projecting ridges over at least a portion of its length and in which the cross section of each ridge is generally in the shape of a trapezium having a base which tapers outwardly gradually from the direction of the head of the punch to a frustum the axis of which coincides with the axis of the punch.

2. A punch as claimed in claim 1 in which the frustum of the punch is defined by an opening angle within the range of 1 to 2.

3. A punch as claimed in claim 1 in which the opening angle of the frustum is greater than 2.

4. A punch as claimed in claim 1 which includes means for rotating the punch.

5. A punch as claimed in claim 1 in which the ridges are spaced one from the other axially along the punch by an amount whereby the vertical projection of the base of one ridge comes within the ridge immediately beneath it along a given generatrix of the punch.

6. A punch as claimed in claim 1 in which the ridge has a height within the range of 0.2 to 0.5 mm and in which the outward taper from the head of the punch is at an angle of about 25. 

1. A punch for manufacturing flexible metal tubes of frustoconical shape from a metal blank by inverse-impact extrusion in which the punch has axially spaced helical projecting ridges over at least a portion of its length and in which the cross section of each ridge is generally in the shape of a trapezium having a base which tapers outwardly gradually from the direction of the head of the punch to a frustum the axis of which coincides with the axis of the punch.
 2. A punch as claimed in claim 1 in which the frustum of the punch is defined by an opening angle within the range of 1* to 2*.
 3. A punch as claimed in claim 1 in which the opening angle of the frustum is greater than 2*.
 4. A punch as claimed in claim 1 which includes means for rotating the punch.
 5. A punch as claimed in claim 1 in which the ridges are spaced one from the other axially along the punch by an amount whereby the vertical projection of the base of one ridge comes within the ridge immediately beneath it along a given generatrix of the punch.
 6. A punch as claimed in claim 1 in which the ridge has a height within the range of 0.2 to 0.5 mm and in which the outward taper from The head of the punch is at an angle of about 25*. 